A magnetic recording process includes applying an initial magnetic field to magnetize a magnetic recording medium and positioning a ferromagnetic mask over the magnetic recording medium. The ferromagnetic mask has a tooth which shields a portion of the magnetic recording medium in order to maintain the initial magnetic field in the portion. The process also includes applying a biasing magnetic field to the magnetic recording medium and applying a recording magnetic field to the magnetic recording medium while applying the biasing magnetic field. The biasing magnetic field is substantially perpendicular to the initial magnetic field and the recording magnetic field is substantially opposite in polarity to the initial magnetic field.
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1. A method for use in recording information on a medium, comprising:
applying an initial magnetic field to the medium; applying a biasing magnetic field to the medium, the biasing magnetic field being substantially perpendicular to the initial magnetic field; and applying a recording magnetic field to the medium while the biasing magnetic field is being applied, the recording magnetic field being substantially opposite in polarity to the initial magnetic field.
25. A disk drive comprising:
a disk having a plurality of concentric tracks which store data; and a print head which transfers data to and from the concentric tracks of the disk; wherein the disk includes servo information that is applied to the disk by: applying an initial magnetic field to the disk; applying a biasing magnetic field to the disk, the biasing magnetic field being substantially perpendicular to the initial magnetic field; applying a recording magnetic field to the disk while the biasing magnetic field is being applied, the recording magnetic field being substantially opposite in polarity to the initial magnetic field. 12. A magnetic recording process comprising:
applying an initial magnetic field to magnetize a magnetic recording medium; positioning a ferromagnetic mask over the magnetic recording medium, the ferromagnetic mask having a tooth which shields a portion of the magnetic recording medium in order to maintain the initial magnetic field in the portion; applying a biasing magnetic field to the magnetic recording medium, the biasing magnetic field being substantially perpendicular to the initial magnetic field; and applying a recording magnetic field to the magnetic recording medium while applying the biasing magnetic field, the recording magnetic field being substantially opposite in polarity to the initial magnetic field.
2. The method of
the initial magnetic field orients magnetic grains in the medium towards a first direction; the biasing magnetic field orients the magnetic grains towards a second direction that is perpendicular to the first direction; and the recording magnetic field orients the magnetic grains towards a third direction that is opposite to the first direction.
3. The method of
the first direction comprises an X direction in a three-dimensional Cartesian XYZ coordinate system; the second direction comprises a Z direction in the three-dimensional Cartesian XYZ coordinate system; and the third direction comprises a -X direction in the three-dimensional Cartesian XYZ coordinate system.
4. The method of
5. The method of
6. The method of
positioning a mask over the medium, the mask having a tooth which shields a portion of the medium underneath the tooth in order to maintain the initial magnetic field in the portion underneath the tooth.
7. The method of
8. The method of
9. The method of claims 8, wherein the ferromagnetic material includes cobalt.
10. The method of
11. The method of
removing the initial magnetic field before applying the biasing and recording magnetic fields.
13. The magnetic recording process of
the initial magnetic field causes magnetic grains in the magnetic recording medium to orient towards a first direction; and the recording magnetic field causes magnetic grains in the magnetic recording medium that are not located underneath the tooth to orient towards a second direction that is different from the first direction.
14. The magnetic recording process of
15. The magnetic recording process of
16. The magnetic recording process of
17. The magnetic recording process of
the initial magnetic field orients magnetic grains in the magnetic recording medium towards an X direction in a three-dimensional Cartesian XYZ coordinate system; the biasing magnetic field orients magnetic grains in the magnetic recording medium towards a Z direction in the three-dimensional Cartesian XYZ coordinate system; and the recording magnetic field orients magnetic grains in the magnetic recording medium towards a -X direction in the three-dimensional Cartesian XYZ coordinate system.
18. The magnetic recording process of
19. The magnetic recording process of
20. The magnetic recording process of
21. The magnetic recording process of
23. The magnetic recording process of
24. The magnetic recording process of
removing the initial magnetic field before applying the biasing and recording magnetic fields.
26. The disk drive of
the initial magnetic field orients magnetic grains in the medium towards a first direction; the biasing magnetic field orients magnetic grains towards a second direction that is perpendicular to the first direction; and the recording magnetic field orients the magnetic grains towards a third direction that is opposite to the first direction.
27. The disk drive of
the first direction comprises an X direction in a three-dimensional Cartesian XYZ coordinate system; the second direction comprises a Z direction in the three-dimensional Cartesian XYZ coordinate system; the third direction comprises a -X direction in the three-dimensional Cartesian XYZ coordinate system.
28. The disk drive of
29. The disk drive of
30. The disk drive of
32. The disk drive of
34. The disk drive of
35. The disk drive of
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This application is a continuation-in-part (and claims the benefit of priority under 35 U.S.C. §120) of U.S. patent application Ser. No. 10/022,566, filed on Dec. 14, 2001, now abandoned.
This invention relates a process for recording information onto a magnetic recording medium.
A magnetic medium contains magnetic particles that can be polarized by application of a magnetic field. The magnetic medium is characterized by a hysteresis curve, which specifies the magnitudes of magnetic fields needed to change the polarization of the magnetic particles. For example, in the hysteresis curve shown in
Information, such as a servo pattern, is recorded onto a magnetic recording medium by placing a mask (having a magnetic shield value of ΔH) over the medium and applying a magnetic field, Ha. The medium is then re-magnetized such that portions of the medium covered by the mask retain their original polarity and portions of the medium that are not covered by the mask obtain a new polarity.
To reduce the occurrences of spurious subpulses, i.e., regions of improper polarity, on the recording medium, the following two conditions should be met:
Ha-ΔH<Hmin, for regions covered by the mask, and
Ha+ΔH>Hmax, for regions uncovered by the mask.
That is, for covered regions (i.e., regions covered by the mask), the difference between the applied magnetic field and the magnetic shield of the mask should be less than Hmin on the hysteresis curve, resulting in few, if any, changes in polarity in those regions. For uncovered regions (i.e., regions not covered by the mask), the sum of the applied magnetic field and the magnetic shield of the mask should be greater than Hmax on the hysteresis curve, resulting in substantial, if not total, changes in polarity.
In general, in one aspect, the invention is directed to a method for use in recording information on a medium. The method includes applying a first magnetic field to the medium, applying a second magnetic field to the medium, the second magnetic field being substantially perpendicular to the first magnetic field, and applying a third magnetic field to the medium, the third magnetic field being substantially opposite in polarity to the first magnetic field. By applying magnetic fields in this manner, it is possible to re-orient magnetic grains on the recording medium and thereby reduce the magnetic field needed to record information onto the medium.
This aspect may include one or more of the following features. The first magnetic field may orient magnetic grains in the medium towards a first direction. The second magnetic field may orient the magnetic grains towards a second direction that is perpendicular to the first direction. The third magnetic field may orient the magnetic grains towards a third direction that is opposite to the first direction. The first direction may be an X direction in a three-dimensional Cartesian XYZ coordinate system. The second direction may be a Z direction in the three-dimensional Cartesian XYZ coordinate system. The third direction may be a -X direction in the three-dimensional Cartesian XYZ coordinate system.
The second magnetic field may have sufficient strength to orient at least some of the magnetic grains at least 10°C towards the Z direction. The second magnetic field may have sufficient strength to orient a majority of the magnetic grains to 45°C±10°C towards the Z direction.
The method may include positioning a mask over the medium. The mask may have a tooth that shields a portion of the medium underneath the tooth in order to maintain the first magnetic field in the portion underneath the tooth. The information may include a servo pattern to be recorded on the medium and the tooth may define a portion of the servo pattern. The mask may be made of a ferromagnetic material, such as cobalt, having teeth that define a servo pattern to be recorded on the medium. Applying the second magnetic field may change a squareness of the medium.
In general, in another aspect, the invention is directed to a magnetic recording process that includes applying an initial magnetic field to magnetize a magnetic recording medium and positioning a ferromagnetic mask over the magnetic recording medium. The ferromagnetic mask may have a tooth that shields a portion of the magnetic recording medium in order to maintain the initial magnetic field in the portion. The method also includes applying a biasing magnetic field to the magnetic recording medium, the biasing magnetic field being substantially perpendicular to the initial magnetic field, and applying a recording magnetic field to the magnetic recording medium while applying the biasing magnetic field, the recording magnetic field being substantially opposite in polarity to the initial magnetic field.
This aspect may include one or more of the following features. The initial magnetic field may cause magnetic grains in the magnetic recording medium to orient towards a first direction. The recording magnetic field may cause magnetic grains in the magnetic recording medium that are not located underneath the tooth to orient towards a second direction that is different from the first direction. The second direction may have a directional component that is opposite to a directional component the first direction. Orienting the magnetic grains in the second direction may include recording information on the magnetic recording medium. Applying the biasing magnetic field may cause magnetic grains in the magnetic recording medium to orient towards a direction that is perpendicular to a direction of the initial magnetic field and the recording magnetic field.
The initial magnetic field may orient magnetic grains in the magnetic recording medium towards an X direction in a three-dimensional Cartesian XYZ coordinate system. The biasing magnetic field may orient magnetic grains in the magnetic recording medium towards a Z direction in the three-dimensional Cartesian XYZ coordinate system. The recording magnetic field may orient magnetic grains in the magnetic recording medium towards a -X direction in the three-dimensional Cartesian XYZ coordinate system.
The biasing magnetic field may have sufficient strength to orient at least some of the magnetic grains to at least 10°C towards the Z direction. The biasing magnetic field may have sufficient strength to orient a majority of the magnetic grains to 45°C±10°C towards the Z direction.
The ferromagnetic mask may define a servo pattern to be recorded on the magnetic recording medium and the tooth may define a portion of the servo pattern. The mask may include plural teeth that define a servo pattern to be recorded onto the magnetic recording medium. The ferromagnetic material may include cobalt. Applying the biasing magnetic field may change a squareness of the magnetic recording medium.
In general, in another aspect, the invention is directed to a disk drive that includes a disk having a plurality of concentric tracks which store data and a print head which transfers data to and from the concentric tracks of the disk. The disk also includes servo information that is applied to the disk by applying a first magnetic field to the disk, applying a second magnetic field to the disk, the second magnetic field being substantially perpendicular to the first magnetic field, and applying a third magnetic field to the disk, the third magnetic field being substantially opposite in polarity to the first magnetic field.
This summary has been provided so that the nature of the invention can be understood quickly. A description of illustrative embodiments of the invention is set forth below.
Like reference numerals in different figures indicate like elements.
Referring to
Process 10 will be described with respect to the magnetic recording medium 11 shown in FIG. 3. Magnetic recording medium 11 may be any type of medium, such as tape or a disk, that is capable of storing data using a magnetic field. As shown in
In this regard, each magnetic grain includes an "easy axis", such as easy axis 14 of grain 12a. In this context, the easy axis of a magnetic grain is an axis on which the poles of the grain lie naturally. The easy axes of the magnetic grains in a recording medium generally lie along the same plane. In the description that follows, this plane is defined to be the Cartesian XY plane, as shown in FIG. 3. That is, the X and Y directions are the horizontal and vertical, respectively, along the recording medium and the Z direction, where applicable, is pointing "out of" and "into" the page on the plane of FIG. 3.
At the start of process 10, magnetic recording medium 11 is polarized so that its magnetic grains are oriented generally towards the same direction. Referring to
Polarization, in this context, does not mean that all of the magnetic grains are polarized in exactly the same manner, i.e., that all the arrows point in exactly the same direction. Rather, as shown in
Referring to
Ferromagnetic mask 17 has a magnetic shield value of ΔH. Ferromagnetic mask 17 prevents a change in polarity of portions of recording medium 11 underneath mask 17 (i.e., covered by mask 17) up to a value of ΔH. In this embodiment, ferromagnetic mask 17 is comprised of teeth 19 that come into contact with recording medium 11. The teeth provide the shielding ΔH in areas of contact with recording medium 11.
In this embodiment, the teeth 19 are arranged on ferromagnetic mask 17 to define a servo pattern (
Referring to
Applying the biasing magnetic field orients the magnetic grains in recording medium 11 towards a Z (in this case, -Z) direction. This is depicted in
Information is recorded onto recording medium 11 by applying (204) a recording magnetic field Ha to the medium. Referring to
Ha-ΔH<Hmin, for regions covered by the mask, and
Ha+ΔH>Hmax, for regions uncovered by the mask.
Applying Hp reduces Hmax, thus increasing the squareness of recording medium 11. "Squareness", in this context, refers to the shape of the medium's hysteresis curve. The closer Hmax and Hmin are to one another, the more "square" the recording medium defined by the curve is. Since Hmax is lower following application of Hp, lower Ha and ΔH values can be used for magnetic recording.
In more detail, magnetic grains that are polarized oppositely to Ha are more difficult to switch during printing than magnetic grains that are offset relative to Ha. Applying Hp to recording medium 11 offsets the magnetic grains relative to Ha. This has the effect of reducing Hmax for the material (since the offset makes it possible to use a smaller magnetic field to switch the polarity of the magnetic grains). Referring to
Process 10 can be used to write servo data to a magnetic disk in a disk drive (not shown). The magnetic disk, in general, contains a plurality of concentric tracks for storing digital data and servo spokes for storing servo information. The servo information is stored on the tracks of the disk via, e.g., process 10, in the form of magnetic polarity transitions induced into a magnetic layer covering the disk.
During operation of the disk drive, the disk is rotated about an axis by a spin motor at a substantially constant angular speed. To perform a transfer of data with the disk, a transducer, known as a print (or "recording") head, is centered above a track of the rotating disk. Once centered, the head can be used to transfer data to the track (during a write operation) or to transfer data from the track (during a read operation). During writing, a write current is delivered to the centered head to create an alternating magnetic field (the recording magnetic field noted above) in a lower portion of the head that induces magnetic polarity transitions onto the track. During reading, the centered head senses magnetic fields emanating from the magnetic polarity transitions on the moving track to create an analog read signal representative of the data thereon.
The invention is not limited to the specific embodiments described above. For example, the invention is not limited to recording servo patterns or to recording the servo patterns onto disks or tape. The invention is not limited to using a ferromagnetic mask. Any type of mask that will provide a magnetic shield can be used. The invention is not limited to the specific geometries and/or to the directions of the magnetic fields described herein. These may be varied so long as their counterparts are varied correspondingly in accordance with the teachings set forth herein.
Other embodiments not described herein are also within the scope of the following claims.
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